Update: The leader of Catalonia has said Spain is showing a "totalitarian attitude" with the arrests of Catalan officials and civil servants, and vowed to go ahead with an independence referendum despite legal warnings not to do so.

Carles Puigdemont appeared with members of his cabinet following several arrests in an ongoing operation by Civil Guard agents.

Those arrested include a top official managing the region's economic affairs.

Mr Puigdemont said the police operations are unlawful and are aimed at preventing Catalans from voting on October 1.

The vote has been suspended by Spain's Constitutional Court while judges consider the central government's claims that it is illegal.

Earlier: Spanish police have arrested 12 people in raids on offices of the regional government of Catalonia as a crackdown intensifies on the region’s preparations for a secession vote that Spain says is illegal.

Today’s raids mostly targeted the region’s economic and foreign departments as Spanish authorities worked to halt all preparatory moves for the planned October 1 referendum, it was reported.

Hundreds of people gathered to protest against the raids and shout pro-independence slogans outside offices in the region’s capital, Barcelona.

The Catalan regional government confirmed Josep Maria Jove, secretary general of economic affairs, was among those arrested.

Police and judicial authorities would give no details on the operation, saying a judge has placed a secrecy order on it.